Method of oxidizing a secondary alkyl-substituted toluene

ABSTRACT

AN OXIDATION PRODUCT COMPRISING AN OILY LAYER CONTAINING A TERTIARY HYDROPEROXIDE OF A SECONDARY ALKYL TOLUENE AND AN AQUEOUS LAYER CONTAINING A SODIUM OR POTASSIUM SALT OF A SECONDARY ALKYL BENZOIC ACID IS OBTAINED BY REACTING A SECONDARY ALKYL TOLUENE WITH OXYGEN IN THE PRESENCE OF WATER AND A CARBONATE OR BICARBONATE CONTAINING SODIUM OR POTASSIUM IN AN AMOUNT OF 0.12 ATOMIC EQUIVALENT OR MORE PER MOLE OF THE SECONDARY ALKYL TOLUENE, OR A MIXTURE THEREOF, OR IN THE PRESENCE OF WATER AND A MIXTURE OF SALTS OBTAINED BY REPLACING UP TO 90% OF SAID CARBONATE OR BICARBONATE WITH A SODIUM OR POTASSIUM SALT OF A SECONDARY ALKYL BENZOIC ACID, UNTIL THE CONCENTRATION OF HYDROPEROXIDE IN THE OILY LAYER FORMED HAS BECOME 15-25% BY WEIGHT OR MORE. WHEN THE TERTIARY HYDROPEROXIDE IN THE OILY LAYER IS CLEAVAGED ACCORDING TO AN ORDINARY PROCEDURE BY USE OF AN ACIDIC CATALYST, CRESOLS ARE OBTAINED. WHEN THE SECONDARY ALKYL BENZOIC ACIDS IN THE AQUEOUS LAYER ARE FURTHER OXIDIZED, BENZENE DICARBOXYLIC ACIDS ARE OBTAINED.

United States Patent Oflice 3,647,866 Patented Mar. 7, 1972 US. Cl. 260524 R Claims ABSTRACT OF THE DISCLOSURE An oxidation product comprising an oily layer containing a tertiary hydroperoxide of a secondary alkyl toluene and an aqueous layer containing a sodium or potassium salt of a secondary alkyl benzoic acid is obtained by reacting a secondary alkyl toluene with oxygen in the presence of water and a carbonate or bicarbonate containing sodium or potassium in an amount of 0.12 atomic equivalent or more per mole of the secondary alkyl toluene, or a mixture thereof, or in the presence of water and a mixture of salts obtained by replacing up to 90% of said carbonate or bicarbonate with a sodium or potassium salt of a secondary alkyl benzoic acid, until the concentration of hydroperoxide in the oily layer formed has become -25% by weight or more. When the tertiary hydroperoxide in the oily layer is cleavaged according to an ordinary procedure by use of an acidic catalyst, cresols are obtained. When the secondary alkyl benzoic acids in the aqueous layer are further oxidized, benzene dicarboxylic acids are obtained.

BACKGROUND OF INVENTION Field of the invention Prior arts At present, cresols are consumed in large quantities 'as starting materials for preparation of synthetic resins, agricultural chemicals and the like. Cresolshave chiefly been obtained by extraction using petroleum or coal tar as astarting material. Further, benzene dicarboxylic acids, i.e. phthalic acid, terephthalic acid and isophthalic acid, are'important compounds as starting materials of synthetic fibers and synthetic resins, and hence are demanded in enormous amounts. The benzene dicarboxylic acids are chiefly prepared at present by the oxidation of xylenes.

Methods for producing phenol by oxidizing isopropylbenzene to form hydroperoxide and then cleavaging said hydroperoxide to phenol and'acetone have been wellknown heretofore. However, when these methods for the production of phenol were applied to the production of cresol, the following disadvantages have been found:

(1) If a secondary alkyl toluene is oxidized under the known conditions for the oxidation of a secondary alkyl benzene, the reaction rate is lower than in the case of the secondary alkyl benzene.

(2) In forming a cresol by the cleavage of a hydroperoxide, which is an oxidation reaction product of a secondary alkyl toluene, a resinous substance is by-produced to make the subsequent operations difficult. Further, the yield of cresol based on the hydroperoxide is lowered.

These disadvantages are ascribable to the fact that when a secondary alkyl toluene is oxidized, primary and tertiary hydroperoxides thereof are formed. When the methyl group is oxidized, the primary hydroperoxide is formed. When the secondary alkyl group is oxidized, the tertiary hydroperoxide is formed. That is, when cleavaged, the tertiary hydroperoxide gives a cresol and a ketone compound, while the primary hydroperoxide gives a secondary alkyl phenol and formaldehyde. Moreover, the cleavage of hydroperoxides is effected, in general, in the presence of an acidic catalyst, and therefore the formaldehyde reacts with the cresols and the secondary alkyl phenol to form a resinous substance. The above reactions are represented by the following equation:

I E 3 l1 Primary hydroperoxide Acid Tertiary hydroperoxide CH Acid.

Ketone compound Secondary alkyl- Formaldehyde substituted phenol (HCHO) Resinous substance wherein R and R represent individually lower primary alkyl groups.

Many studies have heretofore been effected to inhibit the formation of the primary hydroperoxide by suitably selecting the oxidation conditions. According to the experiments carried out by the present inventors, however, in the oxidation of a secondary alkyl toluene the formation of a primary hydroperoxide was not avoided, even when the oxidation conditions were'varied. That is, in the above oxidation, 70-80% of the oxidized alkyl group was the secondary alkyl group, and it was impossible to inhibit the oxidation of about 30-20% of methyl group. On the other hand, U.S. Pats. 2,728,797 and 2,779,797 disclose processes for preparing cresols in which an extraction step is provided between the oxidation step and the cleavage step in order to remove the primary hydroperoxide, or the primary hydroperoxide is previously decomposed by means of caustic soda, so that the tertiary hydroperoxide may be cleavaged with an acidic catalyst in the absence of the primary hydroperoxide. According to these processes, however, an another and special step should be inserted between the oxidation step and the cleavage step, with the result that economical disadvantages are brought about and the yields of cresols cresol (HCHO) based on the secondary alkyl toluenes are also lowered, that is, the efficiency of utilization of toluene is low. Accordingly, it has been diificult to say that the processes of said United States patents are commercially advantageous processes.

SUMMARY OF THE INVENTION In order to find a method for advantageously producing cresols from secondary alkyl toluenes without any such disadvantages as mentioned above, the present inventors made various studies. As the result, the inventors found that a tertiary hydroperoxide substantially free from a primary hydroperoxide could be obtained not by inhibiting the oxidation of the methyl group of a secondary alkyl toluene or by separating a tertiary hydroperoxide from a primary hydroperoxide, like in the case of the said U.S. Patent, but, conversely, by promoting the oxidation of the methyl group of a secondary alkyl toluene to a carboxyl group via the primary hydroperoxide without decomposition of the tertiary hydroperoxide. That is, the inventors found a method for producing a tertiary hydroperoxide substantially free from a primary hydroperoxide by progressing the oxidation of a secondary alkyl toluene in the presence of water and excess alkali until the concentration of hydroperoxide in the oily layer formed became 20% or more.

According to the above method, the disadvantages due to the by-production of primary hydroperoxide could be removed. However, if the above oxidation reaction was progressed until the concentration of hydroperoxide in the oily layer had reached to 40%, the formation of other byproducts than the primary hydroperoxide, i.e. methyltolylketone, ethyltolylketone, tolyldimethylcarbinol, tolylmethylethylcarbinol, 1,1 methyltolylethylene, or 1,1 ethyltolylethylene, necessarily became vigorous with increasing hydroperoxide concentration.

In order to overcome the above disadvantage, the inventors further advanced their studies. As the result, the inventors have found that all the above-mentioned disadvantages can be removed when the oxidation of a secondary alkyl toluene is effected at 50l50 C. in the presence of water and a carbonate or bicarbonate containing more than a definite amount of sodium or potassium, and said oxidation is progresed until the amount of hydroperoxide in the oily layer becomes 15% by weight or more. That is, when a secondary alkyl toluene has been oxidized in the above manner, no primary hydroperoxide is contained in the oily layer formed after oxidation, and therefore in case the resulting hydroperoxide is cleavaged in the presence of an acidic catalyst, a cresol can be obtained in a high yield. And in the above manner, the byproduced primary hydroperoxide is converted to secondary alkyl benzoic acid which can be further oxidized to benzene dicarboxylic acid. Moreover, the present inventors have found that up to 90% of said carbonate or bicarbonate can be replaced by benzene carboxylic acid salt.

An object of the present invention is to provide a method of oxidizing secondary alkyl toluenes to produce synthetic cresols with advantages.

Other objects Will become clear from the descriptions given below.

In order to achieve the above objects, the present invention provides a method of oxidizing secondary alkyl toluenes, characterized in that a secondary alkyl toluene having the formula,

/n l H R wherein R and R are respectively lower primary alkyl groups, is allowed to react at 50-150 C. with oxygen in the presence of water and of a carbonate or bicarbonate containing sodium or potassium in an amount of 0.12 atomic equivalent or more per mole of said secondary alkyl toluene, or a mixture thereof, or in the presence of a mixture of salts obtained by replacing up to of said carbonate or bicarbonate with a salt of a benzenecarboxylic acid, until the content of hydroperoxide in the oily layer formed has become 15-25% (weight), thereby producing a hydroperoxide having the formula,

and substantially free from a primary hydroperoxide having the formula,

/R K H R and at the same time, converting the primary hydroperoxide to a sodium or potassium salt of a secondary alkyl benzoic acid having the formula,

(IJOOH /R R H R wherein R and R have the same meanings as defined above.

Preferable examples of the secondary alkyl toluenes employed in the present method are isopropyltoluenes secondary butyltoluenes and secondary pentyltoluenes. Particularly preferable is isopropyltoluene, and any isomers thereof, i.e. metaand para-form, are usable,

The oxygen source usable in the present invention may be any of oxygen gas and air. The amount of oxygen-required varies depending on the content of hydroperoxide in the oxidation product.

The carbonate or bicarbonate of sodium or potassium employed in the present method is soda ash, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium potassium carbonate or a mixture thereof.

The amount of the carbonate or bicarbonate ofsodium or potassium employed is such that the amount ;of the sodium or potassium is 0.12 atomic equivalent or more per mole of the secondary-alkyl toluene used.

Experimental data with respect to the relationship between the amount of alkali employed and the yield of cresol based on the amount of hydroperoxide, when cymene is used as a secondary alkyl toluene, are as shown in the following table.

Yieldof cresol based on the amount Amount of sodium (atomic equivalent per mole of cymene): of hydroperoxide Percent (wt.)

From the above table, it is understood that when the amount of sodium is 0.20 atomic equivalent per mole of cymene, the yield of cresol shows such a high value as 95.5%, and even when the amount'of sodium is' 0.12. atomic equivalent, the yield is" 90%. However, if' jt he amount of sodium is 0.10 atomic equivalent, which is lower by only 0.02. atomic equivalent than said 0312 atomic equivalent, the yield is rapidly lowered to 839%.

Further, even when the amount of .the carbonateior bicarbonate of sodium or potassium is increased, noill effect is brought about, and therefore there is'no restriction concerning the upper limit in amount of said carbonate or bicarbonate. In view of the solubility of said compound to water and of the economy, however, it will be needless to explain that there is a limit in the amount of said compound added. What is to be particularly explained here is that in order to achieve the objects of the present method, the presence of sodium or potassium in a definite amount based on the secondary alkyl toluene is necessary, and the concentration of the aqueous solution of the carbonate or bicarbonate within the reaction system is substantially out of the question.

Further, what is to be noted in the present method is the fact that the objects of the present invention cannot be attained if a sodium or potassum hydroxide is used in place of the carbonate or bicarbonate of sodium or potassium. If in place of the carbonate or bicarbonate employed in the present method, a same equivalent of caustic soda or caustic potash is used, the oxidation proceeds quickly but the control of reaction becomes diflicult, the selectivity from the secondary alkyl toluene to cresol is lowered, the amount of by-product is increased, and the yield of cresol based on hydroperoxide is decreased.

The present method can be effectively carried out even when a part of the sodium or potassium in the form of carbonate or bicarbonate is present in the form of a carboxylate. In this case also, the resulting tertiary hydroperoxide is stable and the primary hydroperoxide is converted to the carboxylic acid. Further, during the oxidation reaction of secondary alkyl toluene, an acidic substance is formed, and therefore the residual presence of the carbonate or bicarbonate of sodium or potassium is indispensable in order to maintain the oxidation reaction system in a basic condition. The objects of the invention can be achieved even if up to about 90% of sodium or potassium is used in the form of a carboxylate and the balance of about is used in the form of a carbonate or bicarbonate. Usable as such carboxylic acid is benzenecaroxylic acid having the formula,

(IJOOH RIID wherein R" is a hydrogen atom, a carboxyl group, a methyl group, or a secondary alkyl group of R -CH wherein R and R' are as mentioned above, or an alkylcarbonyl group, a hydroxyalkyl group or alkenyl group derived from the above mentioned secondary alkyl group and n is 1, 2 or 3. Examples of the benzenecarboxylic acid include benzoic, phthalic, isophthalic, terephthalic, trimellitic, hemimellitic and pyromellitic acids. It is, however, needless to say that aromatic carboxylic acids, which have substituents having anti-oxidizing actions such as hydroxyl and amino groups, are not usable. When considered from the industrial viewpoint, it is most advantageous to use carboxylic acids derived from the starting secondary alkyd toluenes. Carboxylic acids obtained by the oxidation of secondary alkyl toluenes include toluic acids, secondary alkylbenzoic acids, and those in which the secondary alkyl groups have been oxidized to alkylketone, hydroxyalkyl, alkenyl and carboxyl groups.

The amount of water employed in the present method is such that the weight ratio of water to secondary alkyl toluene is from 10:1 to 1:10. Particularly, the reaction progresses advantageously when the weight ratio is within the range of from 3:1 to 1:3. I

In the present method, the oxidation is advanced until the amount of hydroperoxide in the oily layer formed in the oxidation product has reached 15-25% by weight.

In the oxidation reaction according to the present invention, the reaction rate becomes higher with increasing reaction temperature. At elevated temperatures, however, the amount of by-product also increases. Generally, therefore, the reaction temperature is 50-150 C., preferably 75 125 C.

The reaction progresses either at atmospheric pressure or under pressure, and the reaction rates increases with increasing pressure. Generally, however, a pressure from atmospheric to 30 kg/cm. is adopted.

The reaction times varies depending on the reaction conditions, but a reaction time of 5 to 70 hours, generally 10-30 hours is sufficient.

Since the reaction is carried out in an unhomogeneous phase comprising a secondary alkyl toluene and water, the use of an emulsifier is preferable, and lauric acid, palmitic acid, stearic acid or the like surface active agent may be used.

The reaction proceeds even in the absence of catalyst, but a catalyst such as cobalt-amine complex salt, phthalocyanine copper or molybdenum disulfide may also be used.

The present method may be effected in any of batchwise or continuous manner.

In effecting the oxidation reaction in a batchwise manner, a secondary alkyl toluene and an aqueous carbonate or bicarbonate solution containing a given amount of sodium or potassium are charged into a reaction vessel, and the mixture is subjected to oxidation reaction. After completion of the reaction, the reaction mixture is allowed to stand to separate an oily layer and an aqueous layer, and then only the oily layer is taken out. Into the reaction vessel, a fresh secondary alkyl toluene is charged to again effect the oxidation reaction, and the aqueous layer is repeatedly used until about of the carbonate or bicarbonate of sodium or potassium in the aqueous layer has converted into secondary alkyl benzoates.

On the other hand, in effecting the oxidation reaction in a continuous manner, a secondary alkyl toluene and an aqueous carbonate or bicarbonate solution of sodium or potassium are fed in definite amounts to an oxidation reaction vessel. Subsequently, an oily layer and an aqueous layer flowing out of the reaction vessel are separated each other and, from the separated aqueous layer, an aqueous solution containing a secondary alkyl benzoate of sodium or potassium is withdrawn in a definite amount each time. Thereafter, an aqueous carbonate or bicarbonate solution containing sodim or potassium in an amount coresponding to the amount of the withdrawn sodium or potassium is added to the remaining separated aqueous layer containing the aforesaid secondary alkyl benzoate, and the mixture is again recycled to the oxidation reaction vessel, whereby the object of the reaction can be achieved.

When the oxidation reaction has been complete, the oily layer readily separates from the aqueous layer. The oily layer comprises unreacted secondary alkyl toluene and a tertiary hydroperoxide thereof. The aqueous layer contains a sodium or potassium salt of a secondary alkyl benzoic acid formed by oxidation of the methyl group of the starting secondary alkyl toluene, and a carbonate or bicarbonate of sodium or potassium or a salt of a benzenecarboxylic acid.

When cleavaged in the presence of a catalyst, the tertiary hydroperoxide is converted into a cresol and an aliphatic ketone. As the cleavage catalyst, there is used such an acidic catalyst as sulfuric acid, perchloric acid, sulfurous acid or acidic ion exchange resin. The amount of catalyst used is 0.05 to 5% by weight based on the amount of hydroperoxide. The reaction temperature is from 50- C., and the reaction time is 15 mintues to 3 hours. The hydroperoxides obtained according to the present process are essentially composed of only tertiary hydroperoxides. When the hydroperoxides are cleavaged, therefore, cresols are obtained in amounts of 90-99% of the theoretical amount, i.e. in substantially quantitative yields.

The aqueous layer is charged with a cobalt, manganese or vanadium system catalyst and is oxidized under such conditions as 200300 C. and 20-50 kg./cm. or it is acidified to separate out a secondary alkyl benzoic acid, which is then taken out of the Water layer. Subsequently, the said acid is oxidized by addition of nitric acid or is treated in an acetic acid solvent at 150-250 C. under 5-30 l g./cm. in the presence of a cobalt or manganese system catalyst to form isophthalic acid or terephthalic acid.

Composition of o-, mand p-isomers of the alkyl toluene does not change in the formation of cresols and phthalic acids in the present invention.

The conventional process for the oxidation of secondary alkyl toluene have intended to inhibit the oxidation of methyl groups of the secondary alkyl toluenes, or have adopted a step of separating tertiary hydroperoxide from primary hydroperoxides which have been formed by the oxidation of said methyl groups. In contrast thereto, the present invention is concerned with a method in which the secondary alkyl groups of secondary alkyl toluenes are oxidized to tertiary hydroperoxides and, at the same time, the primary hydroperoxide which is formed by the oxidation of methyl group thereof is also oxidized to carboxyl group to obtain secondary alkyl benzoic acid without the decomposition of the tertiary hydroperoxide. Consequently, hydroperoxides which give cresols in high yields in the presence of acidic catalyst, and secondary alkyl benzoic acids which give benzene dicarboxylic acid by further oxidation can be produced simultaneously. According to the oxidation method of the present invention, 90% or more of the starting secondary alkyl toluenes can be converted into cresols and isophthalic and terephthalic acids. Further, it may be said that in accordance with the present method, the position of said toluene as starting materials for the production of cresols and benzene dicarboxylic acids, which are main materials in the field of chemical industry, has been further eletvated. Moreover, the fact that benzenecarboxylates are usable in the present method is a great advantage and further enhances the value of the present invention. That is, it has become possible that the aqueous layer, is repeatedly used until about 90% of said carbonate or bicarbonate contained therein has been consumed due to c-arboxylic acid formed by the oxidation reaction. As the result, the aqueous layer can be repeatedly used several times to ten several times, in general, though said times vary depending on the oxidation reaction conditions, and thus the proportion of the carbonate or bicarbonate of sodium or potassium, which proportion occupies the production costs of cresols, can be reduced to a great extent. In addition, the repeated use of the aqueous layer without removing by-produced carboxylates not only makes it possible to stabilize the resulting tertiary hydroperoxides to increase the yields of cresols, but also makes accurate the formation of secondary alkyl benzoic acid derivatives, which are starting materials of benzene dicarboxylic acid employed for the production of synthetic resins and synthetic fibers. If the repeated use of the aqueous layer is impossible, only a small amount of secondary alkyl benzoic acid is separated after neutralizing a large amount, per unit of the aqueous layer, of the carbonate or bicarbonate of sodium or potassium. In contrast thereto, if the repeated use of the water layer is possible, a'large amount of secondary alkyl benzoic acid can be separated after neutralizing a small amount of the carbonate or bicarbonate of sodium or potassium, and thus the yield of secondary alkyl benzoic acid per unit of the aqueous layer can be increased.

The present invention is illustrated in detail below with reference to examples, but it is needless to say that the examples are merely illustrative and by no means limit the scope of the invention. In the examples, all the parts are by weight.

8 EXAMPLE 1 Into an autoclave provided with a stirrer, an air-blowing pipe, a gas-outlet pipe, a thermometer and a condenser, parts of cymene, 9 parts of soda ash, 250 parts of water and 0.2 part of palmitic acid were charged, and the mixture was vigorously stirred. Subsequently, the mixture was allowed to react, while injecting air, for 10 hours under the conditions of 100 C. and 15 lQg./cm. After completion of the reaction, the reaction liquid was separated to obtain 99 parts of an oily layer and 265 parts of aqueous layer. The oily layer contained 78 parts of unreacted cymene and 20.3 parts of hydroperoxide. The concentration of hydroperoxide in the oily layer was 20.5%. In addition thereto, up to 0.5 part of methylacetophenone and tolyldimethylcarbinol were also observedin the oily layer. This oily layer was charged with 0.1 part of concentrated sulfuric acid and was heated at 60 -65 C.'for1 hour, whereby the hydroperoxide was clealvaged to obtain 12.8 parts of cresol and 6.8 parts of acetone. The yield of cresol based on the hydroperoxide was 97%, while that of the acetone was 96%. i

On the other hand, the aqueous layer was acidified with sulfuric acid and a separated oily layer was'extracted with toluene to obtain 6.4 parts of cuminic acid (isopropyl benzoic acid). In this cuminic acid layer, acetylbenzoic acid was contained, the toluic acid, isophthalic acid and terephthalic acid were also detected, though the amounts thereof were extremely slight. To this cuminic acid mixture, 20 parts of acetic acid and 1 part of cobalt acetate were added. The resulting mixture was fed to an autoclave and was subjected to oxidation reaction for 15 hours under the reaction conditions of 180 C. and 20 kg./cm. After completion of the reaction, the autoclave was cooled, and then the reaction product wastaken out and was filtered to obtain 5.1 parts of isoand terephthalic acids. The yield of said phthalic acids based on the by-produced cuminic acids was 78%. About 76% of the reacted alkyl group of cymene was the isopropyl group and about 24% was the methyl group.

Substantially the same results as above were obtained, as well, when 14 parts of sodium bicarbonate was used in place of 9 parts of soda ash.

EXAMPLE 2 Into a pressure, continuous oxidation reactor provided With a stirrer, an air-blowing pipe, a gas-outlet pipe, a thermometer and a condenser, 100 parts/hr. of cymene, 0.1 part/hr. of stearic acid, 12 parts/hr. of potassium carbonate and parts/hr. of water were fed, and oxidation reaction was initiated, while blowing air, at a temperature of 95 C. under a pressure of 20 kg./cm. Thereafter, the reaction product was taken out at a rate of 296 parts/hr., while controlling the average retention time in the reaction system to 10-12 hours. The reaction product was composed of 100 parts of an oily layer and 196 parts of an aqueous layer. After withdrawing 39.2 parts of the aqueous layer, 2.4 parts of potassium car: bonate and 36 parts of water were added to the remaining aqueous layer. The thus prepared aqueous layer was recycled at a rate of 195.2 parts/hr., together with 100 parts/hr. of cymene, to the oxidation reactor to effect continuous oxidation reaction. After the reaction system had reached an equilibrium state, 20.4 parts of hydroperoxide and 79 parts of unreacted cymene were detected in 100 parts of an oily layer flowing out of the reactor. Further, 4.5 parts of cuminic acids were detected in 39.2 parts of the withdrawn aqueous layer. The oily layer was cleavaged under the same reaction conditions as in Example 1 to obtain 12.6 parts of cresol and 6.7 parts of acetone. The yield of cresol based on the reacted cymene was 74.6%, whereas the amount of a substance recovered as cuminic acids was 17.5% based on the reacted cymene. From this result, it was understood that more than 90% of the consumed cymene has been effectively utilized. 7

4.5 parts of the cuminic acids were charged into 29 parts of 30% nitric acid, and the mixture was heated to 100-103 C. for 20 hours. After completion of the reaction, the reaction system was cooled, and the reaction product was filtered, washed with water and dried to obtain 4.1 parts of yellowish white isoand terephthalic acids, yields 90%.

EXAMPLE. 3

Into the same reactor as in Example 1, 100 parts of secondary butyltoluene, 300 parts of water, 7.5 parts of soda ash and 0.2 part, of palmitic acid were charged. The mixture was allowed to react for 18 hours, with stirring and while blowing air, at a temperature of 110 C. under a pressure of 20' kg./cm. Thereafter, the reaction liquid wastaken out and was separated to obtain 99 parts of an oily layer and 310 parts of an aqueous layer. The oily layer contained 82 parts of unreacted secondary butyltoluene and 16.8 parts of a hydroperoxide, and the aqueous layer contained 4.1 parts of secondary butylbenzoic acid. From the oily layer, 70 parts of unreacted secondary butyltoluene was removed by reduced pressure distillation. To 29 parts of the thus concentrated oily layer, 0.1 part of concentrated sulfuric acid was added, and the mixture was reacted at 55-65 C. for 1 hour to obtain 9.8 parts of cresol and 6.4 parts of methylethylketone. The yield of cresol based on the hydroperoxide was 97%, and the yield of methylethylketone was 95%.

310 parts of the aqueous layer and 0.5 part of manganese dioxide were charged into an autoclave, and the mixture was subjected to oxidation reaction for hours, while bubbling air, under the reaction conditions of270 275 C. and 80 kg./cm. After completion of the reaction, the reaction liquid was taken out and was adjusted to pH 2 by addition of sulfuric acid. Subsequently, deposed isoand terephthalic acids were separated by filtration, were washed with methanol and with water, and were then dried to obtain 3.1 parts of isoand terephthalic acids, yield 74%.

What is claimed is: 1

1. A method for oxidizing, by reaction with oxygen, a secondary alkyl, toluene represented by the formula,

wherein R and R respectively represent lower primary alkyl groups, characterized in that the secondary alkyl toluene is reacted with oxygen at 50-l50 C. in water and in the presenceof a carbonate or bicarbonate of sodium. or potassium which contains sodium or potassium in an amount of at least 0.12. atomic equivalent per mole of said secondary alkyl toluene, or a mixture thereof, or in the presence of a mixture of salts of sodium or potassiurnwhich is obtained by replacing up to 90% of sodium or potassium in the form of said carbonate or bicarbonate with one in the form of a sodium or potassium salt of a benzene-carboxylic acid having the formula,

wherein R is a hydrogen atom, a carboxylic group, a methyl group, or a secondary alkyl group of carbonyl group, a hydroxyalkyl group or alkenyl group derived from the above mentioned secondary alkyl group,

10 and n is 1, 2 or 3, until the content of hydroperoxide in the oily layer formed has become 15-25% (weight), thereby obtaining a hydroperoxide represented by the formula,

wherein R and R are as mentioned above in an oily layer, and sodium or potassium salt of a secondary alkyl lbenzoic acid represented by the formula,

(IJOOH wherein \R and R are as mentioned above, in an aqueous layer.

2. A method according to claim 1, wherein the lower primary alkyl group represented by R is a methyl group and the lower primaryalkyl group represented by R is a methyl or ethyl group.

3. A method according to claim 1, wherein the amount of sodium or potassium is 0.12-0.60 atomic equivalent per mole of the secondary alkyl toluene.

4. A method according to claim 1, wherein the amount of water is 1/10-10/1 by weight based on the amount of the secondary alkyl toluene.

5. A method according to claim 1, wherein the reaction is effected in the presence of palrnitic acid or stearic acid as an emulsifier.

6. A method according to claim 1, wherein the aqueous layer is repeatedly used until up to of the carbonate or bicarbonate of sodium or potassium or a mixture thereof, which is fed in the oxidation reaction initially and has sodium or potassium in an amount of at least 0.12 atomic equivalent per mole of said secondary alkyl toluene, is converted to the sodium or potassium salt of the benzenecarboxylic acid.

7. A method according to claim 1, wherein a part of the aqueous layer, which contains the carbonate or bicarbonate of sodium or potassium and sodium or potassium salt of the benzenecarboxylic acid, is withdrawn, an aqueous solution of a carbonate or bicarbonate of sodium or potassium containing sodium or potassium in an amount corresponding to the amount of the withdrawn sodium or potassium is added to the remaining separated aqueous layer, and the resulting mixture is again recycled in the oxidation reaction.

8. A method for producing cresols and ibenzene dicarboxylic acids from secondary alkyl toluenes, characterized in that a secondary alkyl toluene represented by the formula,

wherein R and R are respectively lower primary alkyl groups, is reacted with oxygen at 50-150 C. in water and in the presence of a carbonate or bicarbonate of sodium or potassium which contains sodium or potassium in amount of at least 0.12 atomic equivalent per mole of said secondary alkyl toluene, or a mixture thereof, or in the presence of a mixture of salts of sodium or potassium which is obtained by replacing up to 90% of sodium or potassium in the form of said carbonate or bicarbonate with that in the form of a sodium or potassium salt of a benzenecarboxylic acid having the formula,

OOH

wherein R and R are as mentioned above, in an oily layer, and a sodium or potassium salt of a secondary alkyl benzoic acid represented by the formula,

( IOOH /R K 11 R wherein R and R are as mentioned above, in an aqueous layer; the oily layer containing the hydroperoxide is separated from the aqueous solution, and is cleavaged at 50- 100 C. in the presence of an acidic catalyst to form cresols; and the secondary alkyl benzoic acids in said aqueous solution are oxidized, either in the form of said alkali salts or after acidifying the aqueous solution to convert said alkali salts into the form of a free acid, thereby obtaining benzene dicarboxylic acids.

9. A method according to claim 8, wherein the aqueous layer is repeatedly used until up to of the carbonate or bicarbonate of sodium or potassium or a mixture thereof, which is fed in the oxidation reaction initially and has sodium or potassium in an amount of at least 0.12 atomic equivalent per mole of said secondary alkyl toluene, is converted to the sodium or potassium salt of the benzenecarboxylic acid. I j

10. A method according to claim 8, wherein a part of the aqueous layer, which contains the carbonate or bicarbonate of sodium or potassium and sodium orpotas sium salt of the 'benzenecanboxylicacid, is withdrawn, an aqueous solution of a carbonate or bicarbonate of sodium or potassium containing sodium or potassium in an amount correspondingto the amount" of the withdrawn sodium or potassium is added to the remaining separated aqueous layer, and the resulting mixture is again recycled in the oxidation reaction.

References Cited UNITED STATES PATENTS 3,171,860 3/1965 Codig nola 260-610 3,187,055 6/1965 Armstrong et al. 260-6l0 FOREIGN PATENTS f 1,299,531 6/1962 France 260-524 OTHER REFERENCES iBondarenko et al., Neftekhimiya 6, 423 (1966), V

LORRAINE A. WEINBERGER, Primary Examiner R. GERSTL, Assistant Examiner US. Cl. X.R. 

